Nicholas Castle, a 23-year-old UC Berkeley graduate who taught English with the Peace Corps in rural China, died Thursday.

Mr. Castle, who grew up in Brentwood, died at a Chinese hospital three days after falling ill, said his mother, Susan Castle, who flew to China to be with her son. Doctors aren't certain what the illness was, she said.

"I always called him scary smart," said Susan Castle, a freelance network administrator. "He was all-around smart - he liked everything. I looked on his Kindle when we were there and everything was Kurt Vonnegut; he would read everything."

His father, David Castle, said his son often insisted that they watch movies from the American Film Institute's list of top 100 films.

"We would sit together and we'd watch movies that I didn't get at all," said David Castle, a sergeant with the Brentwood Police Department. "We'd just discuss them and debate. ... But he wasn't arrogant smart, he wasn't condescending."

Mr. Castle wanted a career in U.S.-Chinese diplomacy and was excited when the Peace Corps stationed him in China to teach English, his mother said. He moved to southern China's Guizhou province in July, one month after graduating with degrees in political science and comparative politics.

He acclimated to life in the rural area, where his students often invited themselves over to his home to teach traditional Chinese cooking.

" 'How many (came over)?' I would ask, thinking it would be two or three," Susan Castle said. "And he would say 12 or 15."

His father added, "There are two things I've heard him use the word 'love' with besides family - that was Cal and then when he went in the Peace Corps."

Mr. Castle's body has been flown to Dover Air Force Base in Delaware, where government pathologists will conduct an autopsy.

He is survived by his father, mother and three brothers. Services are pending.